Generally, earth leakage circuit breakers (ELBs) are used to prevent an electric shock of a human body and a fire by earth leakage, or molded case circuit breakers (MCCBs) are used to prevent overcurrent by short circuits and to protect load terminals, in houses, buildings, etc.
The molded case circuit breakers (MCCBs) are used for the purpose of protecting electric wires, and the earth leakage circuit breakers (ELBs) are used for the purpose of protecting a user by detecting whether or not he or she is electrically shocked through an electric circuit when he or she is using an electric device and interrupting an electric power supply.
As described above, although the earth leakage circuit breakers (ELBs) may prevent electric shocks due to earth leakage, and the molded case circuit breakers (MCCBs) may prevent a fire or damage of loads due to overcurrent, there are a variety of electric defects which may not be prevented by the earth leakage circuit breakers (ELBs) and the molded case circuit breakers (MCCBs). Arc faults occupy the largest frequency among the various electric defects.
Arc faults occur at all areas from electric power distribution systems to indoor electric wires, electric power cords, loads (electric or electronic devices). Occurrence of most arc faults is caused by external exposure of coated electric wires due to aging and damage of insulation and coating in electric cables, mechanical and electrical stress resulting from overcurrent, defective connection, excessive damage of insulation and wires, etc. In this case, electric current flows through metallic outer surfaces of electric or electronic devices. Most of the arc faults are not protected by overcurrent circuit breakers or earth leakage circuit breakers which are circuit breakers for wiring.
The reason is because arc faults induce overcurrent quickly, electric or electronic devices are not directly grounded in most cases, or arc faults occur even at a low electric current and high impedance mode.
In addition, arc faults occur to thus cause a high temperature fashion. As a result, the arc faults may be detected and interrupted by ground fault circuit interrupters (GFCIs) only when sufficient leakage current flows through the ground. Further, such interrupters operate only when electric current due to arc faults exceeds parameters of thermal/magnetic structures. As a result, Arc Fault Circuit Interrupters (AFCIs) which can interrupt arc faults are essentially required.
However, since existing general circuit breakers can detect only one electric danger factor, respectively, the respective circuit breakers should be installed in order to detect electric danger factors such as arc faults, overload or overcurrent, and ground faults, to accordingly cause to be troublesome as well as to be economically burdensome. Moreover, the existing circuit breakers do not have any association of the respective danger signals but operate individually. As a result, the existing circuit breakers do not detect risky situations timely and accurately, or misperceive a normal situation as a dangerous situation, to thus frequently malfunction.